The two key times for natural cleansing are the times of transition into spring and autumn.

Dr. Gittleman has created a comprehensive program of internal cleansing, outlined in her book The Fast Track One-Day Detox Diet, that begins with organic foods, features a day of juice fasting, and transitions back to organic food.

"What's the point of getting all those toxins out of your system only to load yourself up again every time you sit down to dinner? All the detoxing in the world won't keep up with the load of chemicals you're consuming if you continue to eat conventionally farmed food," she says.

Juice fasting, preferably with as much organic produce and pure water as possible, provides fiber and nutrients, while making it easy to transition to and from solid foods.

After fasting, Dr. Haas recommends raw or cooked low-starch (low-glycemic) vegetables, including a little sauerkraut to help stimulate digestive function.

"A laxative-type meal including grapes, cherries, or soaked or stewed prunes can also be used to initiate eating [solid foods once again], as they keep the bowels moving," he says.

And consume friendly bacteria in fermented foods like yogurt with active and live cultures or take a quality probiotic product, adds Dr. Gittleman.

Dr. Hass recommends that fasting be done only under the care of an experienced physician, usually one who is a naturopathically trained MD, DO, ND, or DC. It's not recommended for pregnant or lactating women and anyone planning surgery.

In addition, "people with cancer need to be careful about how they detoxify, and often they need regular, quality nourishment," he adds.

"Some people go to extremes with fasting," he warns, "and begin to lose essential nutrients. Excessive detoxification can be a concern; finding balance is the key for each of us."